At our Vancouver veterinary hospital, one of the first things I am often asked by an owner when their pet is diagnosed with lice is whether they will get it too. I am happy to report that the answer is no.

Luckily lice are very host specific, meaning human lice will only affect humans, dog lice affect only dogs, and cat lice affect only cats.

Lice are elongated, flat, wingless insects that can be seen with the naked eye. Lice spend their entire life on the host and infestation is contracted by direct contact with an affected animal or contaminated bedding, combs or brushes.

Life Cycle: Dog or Cat lice spend their entire 21-day life cycle on our pet. They lay eggs (nits) on the shafts of the hair. Nits appear as white flakes on the hair. Unlike dandruff, which moves or falls off when the hair is disturbed, nits are firmly cemented to the hair. A nymph hatches from the ova and goes through 3 molts to become an adult.

lice lifecycle resize

In dogs there are two types of lice: sucking lice and biting lice. In cats there is just biting lice.The sucking louse in dogs are blood suckers so in large infestations in very young and small or old dogs, significant blood loss can occur. In the majority of cases of lice infestation the bites from the lice simply irritate the skin and the main complaint is excessive itchiness, often times associated with excessive “white flakes” on the coat.

sucking lice

Sucking Lice

biting louse

Biting Lice

Treatment: Fortunately lice are susceptible to almost all insecticides. However the nits are resistant to the insecticides so treatment will need to be repeated in 10-14 days to eliminate the nits that hatch after the first treatment.

1) Insecticidal shampoos may be used initially to eliminate the adult lice. Following the shampoo, treat with one of the following insecticides and repeat treatment in 2 weeks.

2) Insecticides to choose from:

Revolution (Selamectin) : Repeat in 2 weeks. This is “off-label” use.

Advantage (Imidacloprid): Repeat in 2 weeks. This is “off-label” use. 0.15% Pyrethrin spray: Use only on animals over 12 weeks of age; Can be repeated every 9 days for 3 treatments.

3) Treat all animals of the same species in the house.

4) Clean and disinfect bedding and grooming equipment.

Wishing you a lice free summer!

Loretta Yuen. D.V.M


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